ARM: VFP tweaks/optimisations. Further address slow FPSCR accesses.

BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com/14121004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14311 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix x64 frame size to accomodate saved XMM registers

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/13881016

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14312 ce2b1a6d-e550-0410-aec6-3dcde31c8c00